These Rare Dive Watches Were Designed to Help Save Lives

SCUBA diving has always been a sport of measurement.

Whether it’s getting a reading on depth, determining the correct gas mixture or recording time spent underwater, accurate calculations can mean the difference between a successful dive and a potentially fatal one.

Because the stakes are so high, the majority of contemporary divers leave little to chance and rely on digital dive computers for both technical and basic dives. But this wasn’t always the case.

Not all that long ago, divers put their faith in dive watches with specially designed dials and bezels. These tools, used in conjunction with depth charts, helped divers measure their no-decompression time (the time they could spend at a particular depth without needing to decompress before ascending) as well as their decompression time (time spent at depth stages before resurfacing).

These types of specialized dive watches, often referred to as decompression timers, featured abbreviated — and often very colorful — dive tables on their dials that effectively told a diver how long to stop at each depth when making their decompression stops on the way to ascending.

Making the appropriate decompression stops is essential when completing a dive, as it allows the diver to off-gas the excess nitrogen their blood has absorbed during the dive. Failure to do so can result in decompression sickness, better known as the bends, which can be dangerous.